Photoconductive elements for use in electrophotographic imaging are well known. Photoconductive elements are used for conventional optical exposures such as those commonly utilized in photocopiers and photoduplicators. Photoconductive elements are also known which can be imaged either by an array of light emitting diodes (LEDs) or by scanning laser exposure. With either LED or laser exposure, the image to be reproduced has been converted by a variety of means into a stream of digital information. Machines which employ digitally imaged photoconductive elements are generally referred to as printers, sometimes laser printers.
The lasers or LEDs which are used to carry out digital imaging generally emit light in the near-infrared (near-IR) region of the spectrum, defined for the purposes of this invention as light having a wavelength in the range of about 650 to 900 nm. Accordingly, the photoconductive elements must be capable of absorbing light in this wavelength range. Many near-IR sensitive photoconductive elements exhibit problems affecting their performance. For example, when such elements are imaged with relatively high power near-IR lasers, the near-IR absorbing dye or pigment present in the photoconductive element may fail to absorb all of the incident light emitted by the laser. As a result, the excess, unabsorbed light generates an image artifact generally known as a laser interference pattern (also known as "plywood" or "wood grain" effect).
Other solutions to this problem have included use of a conductive support having a roughened surface as disclosed in Japanese Patent Application Serial Nos. 162975/83, 17 1057/83, 112049/85. Another potential solution is the use of a support having a light scattering layer, on the side opposite the photosensitive layer, which prevents laser radiation from being reflected back to the photosensitive layer thereby causing the laser interference pattern as disclosed in U.S. Pat. Nos. 4,756,993 to Kitatani et al. and 5,051328 to Andrews et al. However, these solutions for the problem of laser interference patterns are not without disadvantages. They introduce further complexity into the formation of the element, lessen the versatility of the element, and decrease the performance of the electrophotographic element. Accordingly, it is an object of the present invention to produce easily manufactured photoconductive elements which largely eliminate laser interference patterns while still maintaining good performance characteristics.